Currently, there is a high demand for transgenic plants that express biotechnologically important protein products at a high or inducible level. Manipulation of crop plants to alter and/or improve phenotypic characteristics (such as productivity or quality) requires the expression of heterologous genes in plant tissues. Such genetic manipulation has become possible by virtue of two discoveries: the ability to transform heterologous genetic material into a plant cell and by the existence of promoters that are able to drive the expression of the heterologous genetic material.
Among the most commonly used promoters are the nopaline synthase (NOS) promoter (Ebert et al., Proc. Natl. Acad. Sci. U.S.A. 84:5745-5749 (1987)); the octapine synthase (OCS) promoter, caulimovirus promoters such as the cauliflower mosaic virus (CaMV) 19S promoter (Lawton et al., Plant Mol. Biol. 9:315-324 (1987)); the CaMV 35S promoter (Odell et al., Nature 313:810-812 (1985)), and the figwort mosaic virus 35S promoter (Sanger et al., Plant Mol. Biol. 14:433-43 (1990)); the light inducible promoter from the small subunit of rubisco (Pellegrineschi et al., Biochem. Soc. Trans. 23(2):247-250 (1995)); the Adh promoter (Walker et al., Proc. Natl. Acad. Sci. U.S.A. 84:6624-66280 (1987)); the sucrose synthase promoter (Yang et al., Proc. Natl. Acad. Sci. U.S.A. 87:4144-4148 (1990)); the R gene complex promoter (Chandler et al., Plant Cell 1:1175-1183 (1989)); the chlorophyll a/b binding protein gene promoter; and the like.
The identification and isolation of regulatory elements useful for strong or inducible expression of genes in microorganisms and plants would be beneficial in the development of commercial varieties of transgenic plants.